Source: Beartracks 2026 Issue 1, Jared Yates
As we know, our airplanes don’t get “Annuals”, they get yearly Condition Inspections. The way it has always been, if we build an airplane with an Experimental/Amateur-Built (E/AB) airworthiness certificate, the builder could apply for a Repairman’s Certificate under 65.104. The holder of a certificate of that type could complete the condition inspection for that specific airplane, listed by registration number, even if the repairman no longer owned the airplane. In my case, the repairman certificate for our first Bearhawk isn’t good for much at all, since the plane was destroyed in a fire. When we had the good fortune to purchase a completed and flying Bearhawk from our friend Mark to replace the first one, I was not eligible for a 65.104 Repairman certificate, complicating my yearly Condition Inspection needs.
This year at Airventure when the new MOSAIC rules were announced, a very nice bonus regulatory change came along in the package. A person who owns an E/AB airplane could obtain a Light Sport Repairman’s Certificate with an Inspection rating under 65.107, and then that person could perform the Condition Inspection on any E/AB airplane that he owns. Notably, this isn’t just the newly-classified Light Sport airplanes, but any homebuilt, regardless of its performance capabilities. Also, while the Repairman must own the plane to do the inspection, any future planes that he purchases are also eligible for a Condition Inspection, without any additional classes. Before Oshkosh was over, I was in contact with Carol Carpenter at Rainbow Aviation to get myself into one of the 16-hour weekend classes so I could obtain the LSR-I certificate. I wasn’t alone, and Carol said her phone was ringing off the hook. In short order we secured the next open travelling slot and our local EAA Chapter 731 hosted the class in North Carolina in November 2025.
The class itself was still mostly oriented towards the type of airplanes that we used to call LSAs, with Rotax engines and sail cloth covering. I did learn some things though, and most importantly, I got the completion certificate for the course and forwarded it to my local FAA FSDO. Unfortunately, the “big” FAA had not yet issued guidance to the local FAA guys about how to issue these certificates, so we entered a brief holding pattern. In early 2026 the guidance finally came along and I was able to obtain the certificate, but I wasn’t quite done yet.
As we know, our E/AB airplanes have “Operating Limitations” that are issued along with the Airworthiness Certificate. Back a few years ago, the FAA combined these two papers into a single document, with the certificate on the first page, and the Operating Limitations language starting right below that. I had gone through the process of updating these documents right after we acquired our second Bearhawk, mainly to update the Phase 1 testing area to its new home in North Carolina, instead of Texas, and to enable transition training. Those operating limitations specifically listed that the Condition Inspection could only be completed by a 65.104 Repairman or by an A&P Mechanic. Most folks will have this language in theirs too, and to be able to complete the Condition Inspection as an LSR-I, we need to have a new Airworthiness Certificate issued again, along with the corresponding new Operating Limitations language.
As it was with the Repairman Certificate, when it came to the Airworthiness Certificate, the “big” FAA had not yet issued guidance to the local FSDO guys about how to execute the update, so I entered another brief holding pattern. Once the guidance was finally released, I had to log in to the FAA’s AWC portal and request a new Airworthiness Certificate, just as a builder of a new Bearhawk would today. This process is similarly tedious to applying for an Airman Certificate using IACRA. It requires some meticulous attention to detail to complete the fields and make sure everything is correct. Thankfully I was assigned a very accommodating and patient FSDO inspector, and together we made it through the process and got the new certificate with the new language.
If you find yourself in a similar situation of owning a homebuilt that you didn’t build, I would highly recommend this process. The weekend course makes you eligible for the LSR-I which allows you to inspect planes, but only while you own them. If time and money are less limited, you can also opt for a longer two-week course, which gets you the LSR-M Maintenance rating. This Maintenance rating allows you to complete the Condition Inspection on planes belonging to others, even on a commercial basis. This is a big rule change compared to the previous requirement to have a full A&P certificate for this kind of work. A two week class is still nowhere near as long as an A&P program. I’m glad to see this regulatory relaxation, and I hope all the folks who get the certificate are able to operate responsibly and within their personal limits, so that maybe we can convince the FAA to give us more freedom and responsibility in the homebuilt world.
Fabricating a Replacement Tailwheel Locking Pin
Source: 2023Q3 Beartracks, Jared Yates
As we know, the Bearhawks (especially the 4-Place and Five) are heavy on the tail when parked. The main wheels sit somewhat forward, so it is very difficult to nose over with a Bearhawk, but the heavy tail is a tradeoff. One Bearhawker years ago told me that he would clean, inspect, and lube his tailwheel assembly every 50 hours. This may be appropriate depending on how the airplane is operated. I try to stick to a schedule of every year or 50 hours depending on which comes first.
Two days before we were to leave for Oshkosh, (isn’t it always?) I noticed that our tailwheel was not locking and unlocking very freely. It turns out that an insect had made a nest inside the tube where the locking pin resides. There was just enough room in the area occupied by the spring, but once we started steering, the nest was broken up and the dirt dispersed in that tube. It didn’t take long for the loose dirt to jam the pin in the locked position. This isn’t a big problem to fix, but it required removing the hex-head screw that connects the locking pin to the bushing that rides on the unlocking cam. When I went to remove it, that little screw snapped off. You can see the results in the lower part of the picture below.
This was not optimal. I knew that Eric Newton at Bearhawk Tailwheels would be happy to sell me a replacement locking pin and screw, but that would take a few days. I used to keep a spare of each, but hadn’t thought to resupply those spares since the fire. If we were going to fly to Oshkosh, I’d have to make new ones. I started with a long grade 5 zinc plated bolt from the hardware store, which had a nice unthreaded shank section. The first step was to drill a new hole to receive the screw. With a milling machine this would be an easy step, but with hand alignment it took two tries to get an acceptably-located hole. The hole needs to be centered, and I found that grinding a tiny flat spot gave the center punch, and subsequent drill bit, a little landing pad. Not having anything like the original screw, I used an AN-3 bolt, so I tapped the hole for fine threads. Once the hole was threaded, I cut the new pin to length and deburred the edges. The next problem was the bushing. I found that a stack of three AN washers looked just about right, and worked great. I added just a little thread locker to the AN bolt, and worked some grease in to keep the pin moving freely. Once it was all back together, I packed the locking pin tubing with grease so that the next insect wouldn’t find it to be an attractive housing vacancy. While it was an inconvenience to have to make the new parts on short notice, I’m thankful that we found the problem at home and not while trying to maneuver in the campground or at a fuel stop while on the trip.
Removing Bugs from the Wind Screen and More
Source: 2020 Q3 Beartracks, Russ Erb
One of the common epithets for our small, personal sized aircraft is “bug smashers”. This is actually based in truth, as since we fly at relatively low altitudes, we are flying at altitudes where birds and bugs also fly. While birds seem to be (mostly) intelligent enough to see an airplane coming and get out of the way (though I have had a few “bird strikes” while driving a car), bugs don’t seem to be blessed with such a traffic collision avoidance system (TCAS), nor could they maneuver very fast anyway. What is the load factor available on a common housefly? Add to this the phenomenon of inertial separation, and the little bug(ger)s don’t stand a chance.
Inertial separation is what makes your bagless vacuum cleaner work. Air molecules have very little mass, and thus can turn a sharp corner rather easily. When your wing leading edge comes approaching at 125 knots, air molecules begrudgingly get out of the way, creating just a little bit of drag before going on their way. However, dirt particles in your vacuum or bugs in the air have significantly more mass than air molecules, and thus have far greater inertia. Because of this greater inertia, it takes far more force to change their velocity.
This is why the dirt just slides along the inside of the cylinder of your vacuum while the air gets sucked to the low pressure area in the center of the vortex. This is why debris gets thrown out of tornados. Most importantly, when a bug finds a leading edge rapidly approaching it, it can’t get out of the way. SPLAT!!
So now that we know why bug remains so quickly and easily decorate the forward facing parts of our airplanes, why do they take so long and are so difficult to remove? Well, like most living things, bug guts are primarily protein and water. What other common household item do you probably have that is also protein and water (that you don’t intend to eat)? Glue! Many types of glue are based on proteins.
Did you ever do papier-mâché where you glued strips of paper together with a mixture of flour and water? When the water dried, the flour proteins held the paper together. In the case of our smashed bug, the bug guts get smashed onto your leading edge as a wet protein paste, which rapidly dries out in the airstream. This leaves the bug guts adhered by a natural protein adhesive. Understanding this is the key to getting the bug guts back off relatively easily.
Bug guts usually get cleaned from windshields fairly regularly, unless you are a test pilot. Test pilots always seem to be talking about control-ling attitude by “pick a bug spot and put it on the horizon” so apparently they like a dirty windshield. However, nobody has bothered to tell the crew chief to leave the bugs on the windshield. As for the rest of the forward facing parts of the air-plane, the bug guts tend to be left on for a much longer period of time, getting constantly dried so as to magnify their adhesive power. These portions only seem to get cleaned when flying is otherwise a bad idea, such as when the winds are 20 gust 30 or a global pandemic is underway.
So armed with this knowledge, what should we do to make cleaning off the buggers at least somewhat easier?
Don’t reach for the petroleum solvents or even household cleaners like Formula 409. Fantastik! may be fantastic, but we’re not trying to clean grease or oil-based residue like you are in the kitchen. The problem we have here is that the bug spots are made up of dehydrated protein, which makes a great adhesive. Hydrated protein (like wet glue) doesn’t make a good adhesive at all. Therefore, Step 1 is to rehydrate the bug guts. Don’t re-animate them—that’s a different issue. Simply spray the bug guts with water or cover them with wet paper towels. Step 2 is tough-er—simply wait. Give the bug guts time to rehydrate. After a few minutes, Step 3 is to wipe off the bug guts with a microfiber towel (sold in large quantities at stores like Costco and Sam’s Club). This should get most of the bugs off. For the buggers that have really cemented themselves in place, you can use some mechanical separation—that is, scrape them off. The perfect tool for this with the perfect hardness is a fingernail. You probably have around ten of them available, conveniently located at the ends of your fingers.
A fingernail seems to be hard enough to scrape the bug guts off but not hard enough to scratch the paint. Products like Plexus are wonderful for cleaning dust off of your windshield, and leave behind a “micro-thin layer of wax” which helps to fill micro-cracks in your acrylic plastic. However, a review of the MSDS shows that it contains no water. Even though Plexus does seem to remove minor bug splats, if you are faced with a semi-opaque covering of bug guts, it is advisable to start by cleaning the windshield with lots of water and a microfiber towel. After cleaning the bug guts off, you can follow up with the Plexus.
Horizontal Stabilizer Struts, Female 5/16″ Threads
A Tale of Two Tail Struts
Source: 2019 Q1 Beartracks, Jared Yates
It was the best of times, it was the worst of times. We had some visitors in town that wanted to go for an airplane ride, so we drove out to the airport and started the usual preparations. Bearhawk folks have known for some time that the airfoil-shaped front support struts for the horizontal stabilizer are a candidate for extra preflight scrutiny. As usual, in my preflight walkaround I grabbed the strut and gave it a tug, but not as usual, the bottom end came off in my hand. The friends were understanding about not getting to go for a ride, or at least they said they were, so I removed the upper bolt still holding the strut on, and went back home.
When the guests were gone I was able to study the broken AN490, which you can see above. This cross section shows that a crack had been developing across the part for some time, with the dull gray part being the section that was holding together at the time of my inspection. Would it have been safe to fly if I had neglected to break it? Probably so. It is said that Bob flew the prototype Bearhawk without the struts before adding them later in testing. It probably would not have broken yet, but it was going to happen sooner or later. At least this was a time of minimal inconvenience.
A few years ago I had contemplated stripping the covering off of the horizontal stabilizer to add wooden strips and give the ribs an airfoil cross section, also adding provisions for an electric trim servo. That project never made it to the top of the to-do list, but since that mod leads to a reduction in the incidence angle, it also requires longer tail struts. This meant I had a pair of spare AN490s on hand, so my plan to fix this was to weld a new one in place of the broken one and carry on.
But as things tend to go, fixing one thing seldom means merely fixing one thing. In recent years we noticed that in cruise flight, the elevator was displaced in a stick-forward position from neutral, based on looking out the window at the counterbalance. This meant we needed less incidence already, even without switching to the profiled rib shapes. If we were going to be making new tail struts, we might as well account for this. I mentioned the part failure to Bob on the phone, and he had some input. First, he reminded me that the tail strut we were using didn’t match his original design. The original does not allow for any adjustment, it’s just made in place to fit. In the early days of the factory, the tail struts were made with welded-in AN490s, which paired with the AN665 female-threaded clevis. The thread size is 1/4×28. One of the problems with this arrangement is that in the welding process, the protective cad plating layer is burned off of the AN490. Threads are extreme stress risers, and this combined with inadequate corrosion protection is not a recipe for success.
Bob had several ideas for an improvement, and here are the two that I liked the best. First, he suggested welding a tube onto the end of the strut, cutting female threads into that tube, and swapping the AN665 out for a clevis with male threads. He also suggested considering a 5/16” thread size, which would be much more durable. With this arrangement, the exposed threads would still have their protective plating, and the cross section area of the clevis inside the threaded area would be much larger.
The first step was to have the parts manager get to work sourcing the supplies, starting with a male threaded clevis with 5/16×24 threads. I couldn’t find one in the aviation catalog, but McMaster Carr carries one as part number 4749T11, $6.05 each. Next we needed a foot of 4130 tubing, 7/16x.095. A few inches would have been fine too, but there wasn’t any in the scrap pile and the minimum order is a foot. The tap and drill were already on hand.
Before starting, I measured the original strut length (36-5/8) to make it easier to guess the new length. Next I cut out the old AN490 with my new portable bandsaw mounted in its Swag Offroad benchtop table (thanks for the tip, Rob Caldwell), and was surprised to find water running out of the tube. The bottom end of the strut is sealed, but apparently it was possible for water to run down the leading edge of the horizontal stabilizer, then between the stabilizer and the strut, then between the layers of the smashed strut end. This would motivate me to weld closed, then re-drill the strut top hole, sealing the struts against future leaking.
Once the slots were cut, I drilled just outboard of the end of the AN490, which liberated the old fitting.
A rotary file made easy work of smoothing the remains. The 7/16 tube fit nicely in that slot, needing only prep for welding, and trimming to length once the welding was done.
Cutting the threads into the tube was a slow process of back and forth every quarter turn. If I had any doubts about how much work the tap was doing, the hot temperature of the tube reminded me.
Next, I needed to reduce the incidence angle by shortening the spacers in the horizontal stabilizer mounting structure. Rather than shorten the old spacers, I made new ones at half length. A folded wire tie held them nicely for painting. In the final installation, I installed a jam nut to keep tension on the threads of the clevis, and I ended up shortening the 7/16 tube by about an inch compared to the image above. In retrospect I should have shortened it before cutting the threads, since that would have saved half an hour of tapping. The end result seems very durable, and initial flight tests after the adjustment suggest that if anything, it may not be enough correction, but at least it is a step in the right direction. I’ll need to fly with a heavier load and further aft CG to see where the elevator falls, but it is currently in trail with the stabilizer at casual local flying weights.
A little more room here would have been helpful. Original spacers are 1/2″
Original spacer
New Spacers Cut
Wire tie holds the new spacers for paint
Quick Tip: Throwing in the Towel to keep things from rolling back
Source: 2018 Q2 Beartracks, Russ Erb
An ongoing problem while building or inspecting under the floor panels is dropped screws, tools, or whatevers that go sliding down the inside of the fabric covering, pulled by the unrelenting force of gravity until they finally reach a location hidden and unreachable by human hands. It seemed that at every annual condition inspection I would find some random piece of hardware back by the tail wheel mount that I hadn’t seen since the previous year’s inspection.
This picture shows one reasonably effective and simple solution that I have found. Simply stuff a towel under the structure against the fabric. The towel does a very good job (if not perfect) of stopping any wayward items before they can disappear into the tail cone. Just be sure to remove the towel before you replace the floor panels.
Flying with the Cowl Door Open (Not Recommended)
Source: 2018 Q1 Beartracks, Jared Yates
It wasn’t something I planned to do, but a few months ago I managed to take off with the right side cowl door unlatched. How could this even be possible, you might wonder? The first link in the chain was obviously an inadequate preflight. It wasn’t a non-existent preflight, but clearly the pilot missed one important step. The second link in the chain that surprised me was that the problem wasn’t obvious as soon as the prop started turning. It must have been closed enough to have partial engagement of one of the camlocks, because everything seemed normal until after I had been flying around for a few minutes. At first it popped up a little, which prompted me to close the throttle and head back to the runway. Shortly after, it opened fully and began whapping itself back and forth a couple times per second.
The pilot on board figured there was not much to be done about it at this point, and resolved that the door would probably separate shortly. A few different slip angles and pitch angles didn’t seem to make any difference, so he focused on landing safely. The mechanic, occupying the same seat as the pilot, was already frustrated about having to mix three batches of paint, and quite dissatisfied with his pilot counterpart. Good news for the mechanic, the door did not separate, which meant being able to salvage the camlocks. This was something the underwriter of the operation (that is, the pilot) was able to appreciate. The other good news about this was that the windscreen was not damaged by a separating cowl door, which would have been bad news for everyone involved. And above all, the door didn’t land on something important on the ground.
After parking back in the hangar, the manager of the parts department ordered a new 3 foot length of hinge (ACS part number 03-000493, MS20257P3) because the old one was starting to crack at the leading edge. The aluminum panel was obviously not salvageable, but fortunately the spare parts warehouse (conveniently behind the tool box in the hangar) had an extra piece of aluminum sheet in stock.
While waiting for the hinge to arrive, the mechanic was able to sort out a strategy for making the holes match on the new cowl door. The problem is that camlock receptacles don’t lend themselves well to any of the hole transferring fixtures in my toolbox. Rather than starting at the hinge line and rolling the cowl door down to try and match the holes, he decided to start at the camlocks and roll the door up to the hinge. The old cowl door was suitable as a template for marking the camlock holes, and for marking the rough outline of the new door. At first the old door was not willing to help with this, being that the old door was all crumpled up. The mechanic beat it flat with a mallet, which yielded complete compliance.
After attaching the new door to the airplane at the bottom (left photo) the mechanic made marks for where the door should be pre-bent. He removed it from the airplane and carried it across the dirt road to the bending die facility, to find a tree of the proper diameter and branchlessness to serve as a die. This prebending got the door pretty close to its final position, and a ratchet strap held it the rest of the way. He then attached the new piano hinge to the blue part of the old cowl top, and match drilled the door and hinge simultaneously, starting at the middle and working outward on alternating sides.
Upon initial construction, the cowling only had camlocks along the bottom. It didn’t seem necessary at the time to add any others, but in the process of making this cowl door, I realized that the nose bowl had deformed a little, just in front of where the hinge line meets it. This explains the gradually degrading clearance between the cowl door and the #1 cylinder, which has worsened over the past few years. In the photo to the left, notice how the light blue lines show a slight V-shape where they should be flat. This problem wasn’t obvious until it came to trimming the leading edge of the new cowl door. When I pressed down on the apex of that blue V, it flexed the nose bowl, changing the geometry of the front of the door. It’s hard to capture with still pictures, but compare the two photos below. One is with no pressure, the other is with downward pressure. Notice how the unpainted part moves aft relative to the nose bowl parts. Or more accurately, the painted parts move forward relative to the unpainted cowl door. When the nose bowl moves forward, it also pushes the aluminum door outward, providing more clearance between the cowl door and the #1 cylinder.
The obvious solution here was to add another camlock in that section of the door, to help support the nose bowl and keep it from moving aft and steepening the V-shaped distortion at the hinge line. In a case where it would have been nice for the mechanic and pilot to actually be two separate people, I pressed down on the hinge from the top while I drilled through the cowl door and into the fiberglass for the camlock. Hopefully this new camlock will help stabilize the cowl and provide a little more distance between the door and the cylinder. In my case, the new camlock is as high as it could be on the bottom half of the nose bowl. Since the fiberglass is not very well-suited to receiving fasteners, I riveted the receptacle to a small tab of .020” 2024, and then attached that tab to the inside of the fiberglass flange with JB weld. The tab also increased the width of the flange just enough so that I can align the wing nut camloc into the breeze. If that doesn’t seem sturdy enough, I might attach a similar tab to the outside of the flange and squeeze some flush rivets through the whole sandwich, to help spread the load out on the fiberglass. If anyone is tempted to only run camlocks along the bottom of the cowl, I’d recommend reconsidering. Most other builders seem to have done it right the first time.
Stubbing Your Bearhawk Toe On The Runway
Source: 2017 Q3 Beartracks, Russ Erb
On 3 July my wife was having new flooring put in the day care room, so she wasn’t available for any family adventures. Therefore, I had arranged with a pilot from work to make good on an offer to take him flying in the Bearhawk. He is part owner in a Cherokee 6. As a bonus, he brought his 6 year old son along who is certified plane crazy. The flight out to L77 went as planned, as did our visit to the Patton museum and lunch. Again using the B-Kool air conditioner to beat the heat, we set out to return to L00. That flight went as planned, right up until the last moments, when it didn’t.
We arrived at L00 around 1400, expecting to land, refuel, and put the airplane away in the hangar. The winds were a left cross at about 10-15 knots. While not fun, I expected no problems because I have successfully landed before with left crosswinds of greater magnitude. I was working with a higher than usual gain on the stick, and managed to softly touch down the left wheel, followed by the right, and was actively working to maintain directional control as the airplane slowed to taxi speed. With the tail wheel on the ground, all was going well until I felt a “thump, thump, thump” on the right side. My first thought was back to 2008, when on the Second First Flight (the one that ended in a ground loop) a similar crosswind blew me off the right side of the runway. Did the right tire fall off the pavement on the right side of the runway? Is my directional control that bad? I looked at the left wheel and it was right on the centerline. The next thought was that the tire had popped, which seemed odd since I hadn’t felt any ridiculous side loads on the landing. Application of higher than normal power for taxi accomplished nothing. “When it takes full power to taxi, put the gear handle down.” But Sir! I don’t have a gear handle! My passenger bailed out of the right door and confirmed that the tire was flat. If you’re going to have a major problem like that, it’s always best to do it at the home ‘drome.
At this point I knew I had an airplane stuck on an active runway, and the first priority was to get it off. I wondered who I could call to come give assistance. Before I could get an answer, I looked to the taxiway at my left and saw a blue pickup truck, with one of our EAA chapter members walking toward me. At that point, I knew we were going to be okay. Turns out he had been sitting there in his truck and had watched the whole landing, right up to the part where it didn’t go as planned!
I shut down the airplane, then hopped out to observe the carnage myself. It was clear that I would need to remove the wheel pant because it covers any and all possible jacking points. I pulled out the tool kit that I carry under the pilot’s seat and started removing screws.
It seems that an airplane on or near a runway with the prop stopped draws a lot of attention. Soon one of the airport residents drove his truck out and offered assistance. He had a furniture dolly and a large floor jack. Thinking the jack was too big, I got a ride to my hangar where I picked up the small floor jack that I normally use for this sort of thing. While we were gone, another resident noticed the excitement and joined in. He brought in a car dolly, which we ultimately used.
When I got back to the airplane, I remembered that my jack only really works if I remove the brake caliper first. We tried manually lifting up under the wing spar, but even three of us couldn’t lift the wheel off the ground. Eventually we found a way to make the large floor jack work, and we were able to get the stubbed toe up high enough to get the car dolly under it.
Wanting to minimize the possibility of further damage to the plane, we started by manually pushing the airplane off of the runway. We got about 800 feet (about a third of the way there) when it became painfully apparent that the rolling friction of the car dolly was so high that we would need multiple rest breaks along the way.
Again, the airport community comes together when there is a disabled airplane. Another lady stopped by and offered to get us some drinking water.
One of the helpers suggested again that we could raise the tailwheel up onto the bed of his pickup, strap it in place securely, and use the truck to pull it back to the hangar. After some discussion and risk mitigation, this is what we did. After getting the airplane to the pad in front of the hangar, we winched it up into the hangar using the normal procedures.
I had previously offered to take a prospective Bearhawk builder flying the next day, but in light of the condition of the airplane I had to reduce the offer to fly to an offer to inspect the airplane.
So what happened to cause this excitement? We’ll never know for sure, but here is my best attempt at an NTSB probable cause investigation. Returning the next day, I removed the offending tire and tube and took the inner tube home. I placed the inflated inner tube in a bathtub full of water. At first nothing spectacular happened, but then I pushed down on the tube to increase its pressure. Air started bubbling quickly out of a hole in the side of the tube, but upon inspection the hole looked like a small chunk of rubber had been ripped out, which I assessed to be damage caused by pinching the tube during the landing. That is, a result of the flat tire, not the cause.
At the same time, I noticed a very small puncture leak in the tread area. It was so small I could not see the actual hole. Based on that, I suspect that during ground operations at L77, a very low use rural airport, I rolled over something that punctured the tire, probably during departure. While flying back at the reduced pressures at altitude, the tire slowly lost pressure. Upon landing, the tire was able to hold some of the load of the airplane, until either the vertical load or side load on the tire caused the tire to be pushed off the bead, unsupported by the low pressure in the tube. At this point, the tire collapsed and the wheel pant touched the runway, supporting most of the aircraft weight, and most likely preventing further damage to the wheel.
There was surprisingly little damage to the wheel pant. My master composites fabricator who helped me build the wheel pants credits that to a modification we made to the pants a few years ago. While addressing some damage to one pant right behind the tire, we had added some significant reinforcing fiberglass to this area in both pants. He thinks that this additional reinforcing gave the strength to support the airplane. He made re-pairs to the tear in the side of the pant, and I decided not to build up the part that was worn down because it is in a location that is very difficult to see, and I already had ground clearance issues with wheel chocks anyway. A spray of paint and it was considered “repaired”.
Several people have commented that I was lucky I didn’t ground loop. I never gave it a thought. I think this was avoided because I was already pretty slow when the tire failed, and because of the crosswind I was already hyper-focused on maintaining directional control.
Oddly enough, this wasn’t really much of an impact on my flying plans. For two or three weeks prior I had been seriously considering replacing both tires, because they had worn to be so out of round that they shook violently on takeoff from about 40 to 60 KIAS—so bad I couldn’t focus on the instruments. This just means I replaced the tires about two weeks earlier than I was planning to.
Since I was changing the tires, by my own procedures that means it was time to repack the wheel bearings. At the last condition inspection I noticed that the brake pads were getting near their minimum thickness, but I figured they would probably last for another year. However, since the brake calipers have to be removed to remove the wheels, I decided to go ahead and install the new brake pads now.
Back in the hangar I remembered that I had created a procedure using a shop crane and a loop of 1/8 inch control cable (or similar wire) to lift the axle when I did the fuel flow test. I now realized that had I been thinking, the best approach to get the stubbed toe up on the dolly would have been to load the crane and cable into a truck and take it out to the runway. I would say that I’ll remember that for next time, but I hope there won’t be a next time.
One problem with removing the brake caliper is that there is nothing to keep the pistons from working their way out. This is especially a problem when the pads are worn, so the pistons are already farther out. If the pistons come out far enough you will have a big mess o’ brake fluid all over the floor. Here a big wrench and a C-clamp take care of the problem.
Three Sigma is all better now, and the new tires just roll smoothly down the runway for takeoff. I didn’t realize how conditioned I had become to the rough ride until I couldn’t figure out when to lift off because I was waiting for the tires to start bouncing!
The Case of the Mysterious Exhaust Valve
Source: 2017 Q2 Beartracks, Pat Fagan
Like the E F Hutton adds of old, when you’re airplane talks, you should really try to listen. My Lycoming O-540 had been trying to tell me it had a problem for almost two years but I could never figure out what it was trying to say. I have a 6 point engine monitor and the problem first surfaced as a CHT variation on #3 cylinder. # 3 always ran about 50 degrees cooler during warm ups but it always came alive and fell in line during the run-up and in the air. Over time I talked about this with many people and got many suggestions but none seemed to resolve the problem.
At my last condition inspection in August # 3 cylinder had a bad leak down test but I was able to bring it back in line by striking the valve spring. Things continued as they had until this year when the cylinder began to run 50 degrees cooler than the others even in the air. It still had a good run-up on the ground but I was starting to sense it wasn’t as smooth in the air as it should be. On a flight last month I was doing my usual power off approach to my home field and felt a distinct roughness from the idling engine. On the ground I did a run-up which checked out fine and I didn’t feel the roughness I thought I had sensed.
I had been looking forward to attending the Bearhawks to Idaho event but I was becoming concerned that back-country flying with this engine mystery wasn’t a smart play. My hand was finally tipped on Memorial Day weekend when I couldn’t get a good run-up out of the engine. Back in the hangar I immediately performed a leak down test on #3 and, good Lord, I had zero compression, with air gushing out the exhaust stack. Thus began the mysterious search into the offending exhaust valve.
My first indication that something was truly weird came when I discovered that if I pulled the prop past TDC on #3, then backed it up to TDC the valve would seat and seal the chamber. Whaaat? That can’t happen. Pull it all the way around the proper direction again and the result was always zero sealing. I pulled both spark plugs and dropped the exhaust manifold so I could look things over with a bore scope and everything looked fine, excellent actually. I applied air to the cylinder again and used my stethoscope to listen to the air rushing out the exhaust port and here’s where it got even weirder.
While probing the valve stem through the exhaust port the rubber hose of the stethoscope touched something which caused the valve to close and the leak down tester to indicate 80/78. Whaaaat? Like in Eric Burden’s song “Spill the Wine” this really blew my mind. I did several more tests, pulling the prop around to #3 TDC, applying air, and probing with the rubber hose and every time got the same result, zero sealing until the rubber hose hit something which caused the valve to close. I finally just stuck my finger in the exhaust port and was stunned to discover that with just finger pressure against the valve stem I could slide the valve back and forth about 1/8”. Far from being a stuck valve, I could silkily bang the thing back and forth with just that finger pressure. Whaaaaat?
Completely baffled I sat down and drew the parts on paper so I could see how they all interacted with each other. The valve rocker pushes on the rotator cap which pushes on the valve spring keepers, which pushes on the valve spring cap which holds the whole shebang together. My conclusion was that the groove the valve spring keepers ride in must have gotten worn over sized. Proud of my analysis I called Bob to get his insight and he burst my bubble by saying what I was experiencing was impossible. The rotator cap pushes against the top of the valve stem, not the keepers, and, by the way, Lycoming valves don’t even have a groove for the keepers. Although Bob didn’t like my explanation he couldn’t offer another one so I hung up the phone still befuddled.
Regardless what was going on in there, it was obvious the cylinder was going to have to come off so a new valve could be installed. I removed the jug and drove it to a shop a few hours from home where they did the service while I waited. He showed me what a new valve should look like compared to the one he removed and by God, Bob was right, the valve stem should be smooth with no groove. I was correct as well though as what I was experiencing was the result of a groove that the keepers were riding in. With the jug reinstalled the engine is now smooth again and all temperatures are in the same range.
To sum up, I learned several things from this. Apparently the cylinder was still firing. Once the rocker arm began to back off the rising piston would close the valve and I would get good compression. Because of the slop, though, it caused the valve timing to be off, and limited how far the valve could open, much like a flat lobe on a cam. That must have accounted for the temperature difference. This was also the first time I had ever done a cylinder change. It looked simple enough and after borrowing the proper wrenches I found that it was quite simple. In fact, the hardest part about it would be writing the check to purchase a new cylinder.
Drill-Powered Tailwheel Towbar
Source: 2016 Q3 Beartracks
Joe Lisanke shares these pictures of a powered towbar that he made up for his Bearhawk. If you can build an airplane, you can probably whip up one of these. Send us a photo of yours for the next quarter!
Recapping Big Tires
Source: 2016 Q1 Beartracks, Mike Creek
Here is a method for adding life to big tires. It was shown to me by a distinguished character with decades of flying experience. This works best before or just when the rubber wears to the point cords are beginning to show. I wouldn’t use this method if the cords are worn through, however as the tires are probably junk at that point. If they are in relatively good condition and not badly worn or weather checked, you may want to give this a try. It is similar to the bed liner method you can find described on several online forums with the difference being that the coating is smooth and results in a thicker urethane coating for longer wear life. This method is really only legitimate for us experimental fliers.
I’ve done it 3 times now over about 3 a three year period with good success. In the photo to the right, a 31-inch tire is on the rotisserie. It is easier to just do them on the plane axle though, but it was too cold at that hangar for that this day.
The basic steps are to:
Jack the plane up so both wheels are at least several inches above the floor and the plane is level in the wingtip to wingtip horizontal plane (photo left). Use jack stands to mitigate having the jacks bleed off over time.
Mount the tire so that it turns freely on the axle. This means removing the brake pads and loosening the axle nut.
Clean the tire with an approved solvent as prescribed by the urethane manufacturer (some people have used lacquer thinner or xylene).
Using 1-inch wide blue 3M masking tape, tape off the tire wear area where the urethane will be applied, and prime the tire surface (right).
Begin rotating the tire at a speed of about 6 rpm.
Prepare the urethane by adding and mixing the catalyst (photo left).
Pour the urethane on the tire in “ropes” that are about pencil diameter moving in a steady motion across the tire. We usually begin in the center and move towards one edge, then return to the center and move towards the other edge. Apply evenly to the entire surface of the tire. While the urethane is being poured, a second person uses a discarded credit card or hotel room key, to further spread and evenly distribute the urethane. They can easily control the application in this way (photo below).
Add as much urethane as you need, being careful to apply it within the allotted time. I’ve applied up to 3 consecutive batches of 1-lb cans each. I could have also mixed them all together and applied – your choice but the single can method allows more time to apply.
Adjust rotation speed based on how the urethane is flowing on the tire. If too fast, it will work its way to the center of the tire and “pile up” there, if too slow it will start flowing across the tapes. Just right, it will stay where you want it. Let the tire rotate for about an hour while the urethane sets up. Do not leave it unattended and keep a watchful eye on it.
Remove the tapes about 30 minutes after you stop urethane application.
The tire should have set up well enough to stop rotating after about an hour, but make sure the coating is firm and won’t flow, before doing so. All times given are approximate and will vary based on temperature. Keep the weight off the tires for at least 24 hours. I’ve flown 24 hours after application and they were ok, however it takes the urethane 7 days to reach full strength so pavement landings prior to that aren’t recommended but can be made if minimal.
I’ve been using a Devcon product called Flexane. A 1-lb can of Flexane costs about $40. Two cans per tire last about 1 year on the Bearhawk with lots of pavement landings, and 29 inch tires.
After a year, I put a 2nd two can coat on top of the first two can coating (after it had worn through in spots) and between this coat and what was left from the first have gone 2 years. So 4-cans per tire has lasted for 3 years. One can of primer lasts long enough to do several pairs. I’ve recently purchased a set of 31’s and coated those with 3 pounds per tire and I’m now flying with those. Used “cores” in good condition can be found for about $500 per tire but can be hard to come by. As the urethane coating wears into the underlying surface, it begins to “feather” at the edges. At that point, you could either recoat or continue flying until the cords begin to show again.
For the rotation method, anything can work, even a hand crank. We began with a $25 BBQ rotisserie motor, but the best method I’ve found is to use a variable speed motor such as this one: http://www.wondermotor.com/Rotisserie_motor.html
I made the end that engages the wheel out of 3 layers of 3/8-inch OSB drilled out then glued together (photo right). If it is just enough diameter to grab the inner 3 bolts on your 10-inch wheels, it will also fit 6-inch wheels. My OSB was a piece of scrap from Home Depot (free) and that is a ½-inch carriage bolt that the last coupler connects to.
The shaft and couplers are from McMaster Carr but the flexible couplers sold by Wonder Motor would be better. The motor shaft is 12mm and that is close enough to 1/2-inch so that is the diameter of the shaft, which is a D-section shaft.
You should achieve good results using this method. The urethane is easy to apply and they turn out well just follow all the way through the directions provided and they’ll look really good when you’re done.